We demonstrate direct detection of individual electron spin states, together with measurement of spin relaxation time ($T_1$), in silicon metal-oxide-semiconductor-based quantum dots (QD). Excited state spectroscopy of the QD has been performed using a charge-sensing technique. $T_1$ of single spin excited states has been done in the time domain by a pump-and-probe method. For an odd and an even number of electrons, we found a magnetic field dependent and invariant $T_1$, respectively.

• Received 1 October 2009

DOI:https://doi.org/10.1103/PhysRevLett.104.096801